The present invention relates generally to electric field delivery to tissue regions. More specifically, the present invention relates to electric field delivery and non-thermal ablation of target tissue regions, including selective ablation of cancerous cells and solid tumors.
Current tissue ablation techniques rely on a high-frequency, hyper-thermia inducing electric current to the tissue of a patient (e.g., human, animal, etc.) as a means to remove unwanted tissue or lesions, staunch bleeding, or cut tissue. There has been increased interest and activity is the area of hyper-thermal ablation as a tool to treat cancer by heat-induced killing and/or removal of tumor tissue.
In hyper-thermal tumor ablation techniques, high-frequency RF (e.g., “RF thermal ablation”) or microwave sources are used to heat tissue resulting in histological damage to the target tissue. In RF thermal ablation techniques, for example, high frequencies, including about 500 kHz and greater, are used to cause ionic agitation and frictional (e.g., resistive) heating to tissue surrounding a positioned electrode. Lethal damage to tissue (e.g., denaturation of tissue proteins) occurs at temperatures in excess of about 47 degrees C., though heat generated near electrodes in RF thermal ablation can reach temperatures up to or exceeding about 100 degrees C.
A number of different cancer ablation methods and devices relying on hyper-thermal ablation or heat-induced tumor tissue destruction have been proposed. One such example includes U.S. Pat. No. 5,827,276, which teaches an apparatus for volumetric tissue ablation. The apparatus includes a probe having a plurality of wires journaled through a catheter with a proximal end connected to the active terminal of a generator and a distal end projecting from a distal end of the catheter. Teachings include a method and probe deployable in a percutaneous procedure that will produce a large volume of thermally ablated tissue with a single deployment.
U.S. Pat. No. 5,935,123 teaches an RF treatment apparatus including a catheter with a catheter lumen. A removable needle electrode is positioned in the catheter lumen in a fixed relationship to the catheter. The treatment apparatuses are taught as being used to ablate a selected tissue mass, including but not limited to a tumor, or treat the mass by hyperthermia. Tumor sites are treated through hyperthermia or ablation, selectively through the controlled delivery of RF energy.
Numerous other methods and devices are taught using hyper-thermal or heat-induced cancer tissue destruction. However, a significant limitation of RF induced, hyper-thermal ablation is the difficulty of localizing the heat-induced damage to targeted cancerous tissue while limiting histological damage and destruction to surrounding healthy, non-target tissue.
Thus, there is a need for minimally invasive ablation techniques that selectively destroy cancerous cells while minimizing damage to healthy tissue.